The present invention relates generally to methods of making an absorbent core for a disposable absorbent garment. More particularly, the invention relates to a method of making an absorbent core comprising one or more laminates in which one of the layers of the laminate or laminates contains a mixture of tow fibers and superabsorbent polymer (SAP),and at least an additional layer of the laminate is a layer that has been cut-and-placed on an outer sheet of the laminate. The additional layer preferably is selected from a wicking layer, storage layer, acquisition layer, wicking/distribution layer, dryness layer, or combinations of these layers, or fragmented layers thereof.
Disposable absorbent garments such as infant diapers or training pants, adult incontinence products and other such products, typically were constructed with a moisture-impervious outer backing sheet, a moisture-pervious body-contacting inner liner sheet, and a moisture-absorbent core sandwiched between the liner and backing sheets. Much effort has been expended to find cost-effective materials for absorbent cores that display favorable liquid absorbency and retention. Superabsorbent materials in the form of granules, beads, fibers, bits of film, globules, etc., have been favored for such purposes. Such superabsorbent materials generally are polymeric gelling materials that are capable of absorbing and retaining even under moderate pressure large quantities of liquid, such as water and body wastes, relative to their own weight.
The superabsorbent material generally is a water-insoluble but water-swellable polymeric substance capable of absorbing water in an amount which is at least ten times the weight of the substance in its dry form. In one type of superabsorbent material, the particles or fibers may be described chemically as having a back bone of natural or synthetic polymers with hydrophilic groups or polymers containing hydrophilic groups being chemically bonded to the back bone or in intimate admixture therewith. Included in this class of materials are such modified polymers as sodium neutralized cross-linked polyacrylates and polysaccharides including, for example, cellulose and starch and regenerated cellulose which are modified to be carboxylated, phosphonoalkylated, sulphoxylated or phosphorylated, causing the SAP to be highly hydrophilic. Such modified polymers may also be cross-linked to reduce their water-solubility.
Adequate absorbency of liquid by the absorbent core at the point of initial liquid contact and rapid distribution of liquid away from this point is necessary to ensure that the absorbent core has sufficient capacity to absorb subsequently deposited liquids. Previously known absorbent cores have thus attempted to absorb quickly and distribute large quantities of liquids throughout the absorbent core while minimizing gel blocking during absorption of multiple doses of liquid.
It is known to provide absorbent laminates comprised of, for example, an upper layer, a lower layer, and a central fibrous layer containing from 50% to 95% by weight SAP. U.S. Pat. No. 6,068,620, the disclosure of which is incorporated herein by reference in its entirety and in a manner consistent with the present disclosure, discloses that the upper and lower layers are comprised of tissue, airlaid fluff pulyor-nthetic non-woven fibrous layers. The upper and lower layers are said to assist in maintaining the integrity of the core, the laminate layered arrangement is said to minimize gel blocking, and the laminate can be folded in various configurations. It also is known to provide a composite absorbent structure having a wicking layer bonded to the absorbent layer with a bonding agent such that the absorbent structure has a Contact Intimacy Ratio. U.S. Pat. No. 6,239,565, the disclosure of which is incorporated by reference herein in its entirety, discloses an absorbent composite having a wicking layer that has a vertical wicking flux value, an absorbent liquid retention layer, and a bonding agent.
It also is known to provide absorbent cores comprised of differing materials in an attempt to maximize comfort and efficiency of the core, and to provide areas having varying degrees of absorbency. U.S. Pat. No. 5,849,002, the disclosure of which is incorporated by reference herein in its entirety, discloses absorbent cores having three zones: (i) one zone for receiving fluids; (ii) one zone for distributing and storing fluids; and (iii) one zone for preventing leakage. U.S. Pat. No. 5,853,402, the disclosure of which is incorporated by reference herein in its entirety, discloses composite absorbent cores comprising at least an absorbent material and a porous resilient material. Other composite, zoned, or multi-component cores are disclosed in, for example, U.S. Pat. Nos. 5,681,300 (blended absorbent core), U.S. Pat. No. 5,882,464 (crimping to join two absorbent structures), U.S. Pat. No. 5,891,120 (varying SAP concentration throughout core), U.S. Pat. Nos. 5,425,725 and U.S. Pat. No. 5,983,650 (multiple fiber free SAP pockets in core), and U.S. Pat. No. 5,922,165 (method of joining outer layers with absorbent core disposed between the outer layers). The respective disclosures of each of these documents are incorporated by reference herein in their entirety.
It also is known to effect synchronous, in-line placement of absorbent core pads on a continuous web of material, as described in U.S. Pat. No. 5,415,716, the disclosure of which is incorporated by reference herein in its entirety. It further is known that graphics can be applied in registration on a moving sheet of material that ultimately is used in an absorbent garment by controlling the timing of placing the discrete graphic material. A number of documents describe placing graphic materials in registration on a moving web, including U.S. Pat. Nos. 6,165,306, 6,149,755, 6,095,218, 6,074,333, and 6,059,710, the disclosures of each of which are incorporated by reference herein in their entireties.
The description herein of advantages and disadvantages of various features, embodiments, methods, and apparatus disclosed in other publications is in no way intended to limit the present invention. Indeed, certain features of the invention may be capable of overcoming certain disadvantages, while still retaining some or all of the features, embodiments, methods, and apparatus disclosed therein.
It would be desirable to provide an absorbent garment having an improved ability to retain fluids and consequently, to prevent leakage. It also would be desirable to provide an absorbent core that includes an increased amount of superabsorbent polymer, (SAP) but at the same time does not suffer from gel blocking to any appreciable extent. It also would be desirable to provide an absorbent core that has the above mentioned characteristics, and in addition has improved acquisition of fluids, and improved distribution and storage of fluids that insult the core.
It is believed that many of these advantages, as well as others not specifically mentioned herein, can be achieved by including an additional layer(s), or fragments thereof in an absorbent composite that includes an upper layer, a lower layer, and a central fibrous layer that comprises a mixture of tow fibers and SAP. It would be desirable to provide a method that can adequately place the additional layer(s), or fragments thereof, in the absorbent composite in the appropriate position to provide the maximum benefit thereof.
It therefore is a feature of an embodiment of the invention to provide a method of making an absorbent garment having an improved ability to retain fluids. It is an additional feature of an embodiment of the invention to provide a method of making an absorbent garment that includes an absorbent composite core having high dry and wet strength for processing and in-use performance, whereby the absorbent composite core includes an upper layer, a lower layer, a central absorbent layer that includes a mixture of tow fibers and SAP particles as a substantial percentage of its basis weight, and an additional layer(s) or fragments thereof. The additional layer is disposed within the absorbent composite core by a synchronous in-line placement thereof onto one of the upper and/or lower layers. The absorbent composite core has good fluid acquisition, distribution, and storage characteristics.
These and other features of the invention can be achieved by a method of making an absorbent composite core that includes providing to a core forming station an upper layer, a lower layer, a central absorbent layer comprising a mixture of tow fibers and SAP, and an additional layer. At least one additional layer is cut and placed on one of the upper and/or lower layer by a synchronous in-line placement method. The central absorbent layer is formed at the core forming station whereby the tow fibers and SAP are mixed and disposed between the upper and lower layer in such a fashion that the additional layer also is disposed between the upper and lower layers. The additional layer is one or more layers selected from an acquisition layer, a distribution layer, an additional fibrous layer optionally containing SAP, a wicking layer, a storage layer, a dryness layer, or combinations and fragments of these layers.
In accordance with an additional feature of an embodiment of the invention, there is provided a method of making an absorbent article that includes providing to a garment forming station a top sheet material and a back sheet material. The method also include preparing an absorbent composite core as described above, and disposing the absorbent composite core between the top sheet material and the back sheet material.
In accordance with an additional feature of an embodiment of the invention, there is provided an apparatus for making an absorbent composite core that includes a composite core forming station, an upper layer supply mechanism for supplying an upper layer to the composite core forming station, and a lower layer supply mechanism for supplying a lower layer to the composite core forming station. The apparatus further includes a tow supply mechanism, a device for opening the tow operatively associated therewith, and a SAP feeding device. The SAP feeding device and the device for opening tow are positioned relative to the composite core forming station, upper layer supply mechanism, and lower supply mechanism such that they respectively feed the SAP and opened tow to the composite core forming station in between the upper layer and the lower layer.
The apparatus further includes a cut-and-place apparatus for effecting synchronous in-line placement of an additional layer or layer. The cut-and-place apparatus is controlled to cut one or more additional layers that are fed to the cut-and-place device at a first speed, and then place the cut additional layer(s) on either the upper layer or lower layer at a second speed that is different from the first speed. The cut-and-place apparatus therefore is positioned relative to either the upper layer supply mechanism or the lower layer supply mechanism to effect placement thereon of the one or more additional layers in such a fashion that the one or more additional layers is disposed between the upper and lower layer at the composite core forming station.
In accordance with an additional feature of an embodiment of the invention, there is provided an apparatus for making an absorbent garment that includes a garment forming station, the above-described apparatus for making an absorbent composite core, and a mechanism for feeding the absorbent composite core to the garment forming station. The apparatus further includes a top sheet supply mechanism for supplying a top sheet material to the garment forming station, and a back sheet supply mechanism for supplying a back sheet material to the garment forming station. The garment forming station forms the absorbent garment by disposing the absorbent composite core between the top sheet material and the back sheet material.
In addition to the foregoing advantages, the absorbent garment having an absorbent composite core comprising one or more SAP-containing central fibrous layers improves the comfort and fit of the garment. Further, due to the thinness of the resulting product, less packaging material is needed for the same amount of product, and shipping and handling costs are lowered.